CPU controlled analog with 'oscillators' amounting to digital pulses being driven to an op amp to kick things off. From there on the signal path is typical digital controlled analog. The JX-10 and MKS-70 use two JX-8P boards each and add an assigner scheme for them. And a nice chorus as usual. The MKS-70 has vastly improved MIDI but see Colin's page above for lots of information.
Many common issues with these. First don't be surprised that the JX-10 can only do MIDI dump from the cartridge. It's true. What possessed them to do this is beyond imagination, I know. Aftertouch tends to go bad. Here is a page describing the problem and a sometimes fix. The feedback resistor also should be modified often in the op amp gaining up the signal from the AT sensor. I seem to recall 3x the value being used. 150K I think. Look for occasional bad solder and lots of dirty switches! Most of the parts themselves are pretty reliable.
Roland may still have some parts for these. And also there are some discrete components that I usually stock.
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